m0useanswered grow question a year ago It would be from the wind, plants also do this when they are Overwatered and Underwaterd
Overwatered = Limp leaves, Stiff stems
Underwatered = Limp leaves, Limp stems
Most of the time you do not want the fan pointing at the plant directly you want it to be moving the air aorund the plant, If there is a setting to lower the intensity on the fan I would enable that, If not point it at the wall just above or below the canopy, the fan will still mix up the air in the tent and move it aorund. If the limpness improves then you know it was from the fan and you need to do this moving forward.
One other option is to block some of the intake on the fan, This will lower the total amount of air it is sucking in and thus lower the amount coming out so its not as strong. You can do this by placing tap or some other things on the front or back of the fans case. You want to check in on this as if it gets dislodged it can clog the fan and be a bigger issues like a fire hazard. Its not something I would recommended because of that unless you can confirm it will not dislodge.
Good Luck!